PowerTip features a very flexible design that is easy to customize, gives you a number of different ways to use the tooltips, has APIs for developers, and supports adding complex data to tooltips. It is being actively developed and maintained, and provides a very fluid user experience.
Features
Straightforward implementation
Supports static tooltips as well as tooltips that follow the mouse
Ability to let users mouse on to the tooltips and interact with their content
Mouse follow tooltips are constrained to the browser viewport
Easy customization
Works with keyboard navigation
Smooth fade-ins and fade-outs
Smart placement that (when enabled) will try to keep tooltips inside of the view port
Multiple instances
Works on any type of element
Supports complex content (markup with behavior & events)
